Replacement of diseased or malfunctioning heart valves requires that the replacement valve be appropriately sized to fit the annulus of the valve that is being replaced. In order to determine the required valve size, the patient's valve annulus needs to be measured. One method of measuring the valve annulus includes taking X-rays of the patient's heart and measuring the diameter of the annulus from the X-rays. However, due to the inaccuracies of X-rays, this method is not very reliable and only an approximate estimate of the valve annulus sizes can be made.
Another method of measuring the valve annulus involves the use of calipers and the like to measure the valve diameter. This method requires that the measurement be made by the surgeon during the valve-replacement procedure. Once the annulus diameter is measured, the valve annulus circumference is calculated and, subsequently, the appropriately-sized replacement valve is determined. This method, however, has several disadvantages. Due to the limited amount of space in the heart, it is difficult to properly located the measurement tools within the heart at the site of the annulus. In addition, a human valve annulus is not perfectly round or circular and, therefore, calculations of valve annulus circumference are imprecise.
U.S. Pat. No. 5,163,955 assigned to Autogenics, assignee of the present invention, describes improved tools for sizing the annulus by use of a series of sized obturators.
Therefore, there is a need for a heart valve annulus measurement device and method whereby a patient's valve annulus may be accurately measured to determine the appropriate replacement valve size. In addition, the device or method should facilitate valve annulus measurement so that the measurement may be performed in a time-efficient manner.